Cellular-system signal-strength analyzers are employed in the prior art to measure and report signal strength information of the communication channels which are used in cellular telephone systems. This information is used to ensure reliable operation over the cellular service provider's coverage area. One current trend in cellular system usage is that an increasing percentage of cellular customers are using portable cellular telephones rather than mobile cellular telephones due to the fact that the usage of portable telephones is not limited to within a vehicle; however, cellular system signal strength analyzers in the prior art have not kept pace principally because the analyzers have been designed for use within a vehicle.
For example, the antenna which is connected to the scanning device which has been designed into signal strength analyzers in the prior art needs to be mounted to a vehicle (window and trunk mounts are the most common), but since portable cellular telephone users can use their phones in buildings, airports, and on sidewalks and pedestrian walkways, the antenna needs to be mounted in a different manner.
Additionally, the navigation technologies that are employed in the prior art for geographic location of the measured signal strength data pertain to vehicle navigation on streets, whereas the technology for navigation in pedestrian areas is quite different. Specifically, common navigation technologies that can be deployed in a vehicle utilize vehicle wheel sensors for speed detection, satellites to determine latitude and longitude, and electronic map-matching techniques for determining a location which is on a street. However, the above-mentioned vehicular navigation technologies cannot be deployed in areas such as within buildings where portable phones may be used. Technologies that utilize range and bearing measurements are best suited to the portable phone domain.
Additionally, the user interface that has been employed in the prior art was not designed to be used in a pedestrian environment where the signal strength analyzer itself must be moved along with the operator of the analyzer. In general, the signal strength analyzers in the prior art utilize a keyboard for input and separate display for output; however, this form of user interface is not practical in a pedestrian environment in which there is no table on which to rest the keyboard and no mounting bracket on which to rest the display.
Additionally, the signal strength analyzers in the prior art were designed to be mounted in a vehicle, and were also designed to derive the power that they need to operate from the vehicle's battery. Since in the pedestrian environment there will neither be a vehicle to mount the signal strength analyzer to, nor a vehicle battery from which power can be derived to operate the signal strength analyzer, a different approach must be taken.
Due to the increasing percentage of portable cellular phone customers, providers of cellular service need to ascertain whether or not adequate cellular service is being provided to all areas in which the portable phones may be used. There are two basic methods for performing this determination. The first method is to use a mathematical model which can indirectly assume cellular system coverage by attempting to accurately predict the propagation of the radio-frequency (RF) energy which is transmitted by the cellular system into the pedestrian areas, and the second method is to empirically measure the actual RF energy in the same areas that the portable phone will be used.
Unfortunately, the first method suffers from the fact that the propagation of RF energy in pedestrian environments cannot be accurately modeled, and is the subject of current research. The main reason for the difficulty in generating an accurate propagation model is due to the many obstacles that exist in pedestrian environments, all of which have different material properties which result in differing amounts of RF energy reflection and absorption. The obstacles, such as interior and exterior walls, partitions, desks, doors, glass, etc., have not even been completely characterized with respect to RF energy interactions due to the complexity of their structures. Even if the obstacles could be completely and accurately characterized and if an accurate mathematical RF propagation model existed, the calculations involved in using the model to predict the propagation of RF energy in pedestrian areas would greatly exceed the computational power of even the fastest computers in the world today. The obstacles in the pedestrian environment are not present in the environment in which mobile phones are used. Since only the atmosphere, buildings and foliage need to be taken into account in the simpler mobile phone environment, fairly accurate RF propagation models have been created which can reliably be used.
Therefore, in the pedestrian environment, cellular service providers need to rely upon empirical, in-field, geographically-located measurements of the RF energy to either verify adequate cellular service or identify problem areas which need attention.